Update CONTRIBUTORS.md

Author: s-celles

CONTRIBUTORS.md

@@ -4,7 +4,7 @@
 - Brian Blaylock - University of Utah Department of Atmospheric Sciences - https://github.com/blaylockbk
 - Ryan Brown - United States Environmental Protection Agency - https://www.epa.gov/
 - daniclaar - Baum lab Applied ecology for impacted oceans - University of Victoria, BC, Canada - https://github.com/daniclaar
-- Sébastien Celles - Université de Poitiers - IUT de Poitiers - https://github.com/scls19fr - project maintainer and co-author
+- Sébastien Celles - Université de Poitiers - IUT de Poitiers - https://github.com/s-celles - previous project maintainer and co-author
 - Filipe Fernandes - Research Software Engineer contractor for SECOORA/IOOS - https://github.com/ocefpaf
 - Daniel Garver - United States Environmental Protection Agency - https://www.epa.gov/
 - Fabien Maussion - Research Centre for Climate at the University of Innsbruck - https://github.com/fmaussion